Method for controlling battery power limit value

ABSTRACT

A method for setting a charging power limit of a battery when charging the battery, including a reference charging power limit setting step of setting a referential predetermined charging power limit, a real-time charging power limit calculation step of calculating a real-time charging power limit in real-time according to a real-time voltage of the battery, a real-time charging power limit setting step of setting a charging power limit of the battery to the real-time charging power limit calculated in the real-time charging power limit calculation step, and a charging power limit restoring step of restoring the real-time charging power limit set in the real-time charging power limit setting step to the referential predetermined charging power limit.

TECHNICAL FIELD

The present invention relates to a method for controlling a batterypower limit.

More specifically, the present invention relates to a method forcontrolling a battery power limit on the basis of a current cellvoltage.

BACKGROUND ART

In general, battery modules having at least one battery cell areelectrically configured in series/parallel to each other, and a batterypack including at least one battery module has a rack battery managementsystem (RBMS) for monitoring and controlling a state of the batterypack. Furthermore, each battery module has a module battery managementsystem (MEMS) for controlling the battery module.

Meanwhile, in a battery pack, battery modules may be connected in seriesto output high power, or battery modules may be connected in parallel toincrease an energy capacity or use time.

With regard to the battery modules connected in series or parallel, amaximum output limit of the battery pack is set according to an SOC andtemperature of the battery modules.

Setting the maximum output limit of a battery pack by measuring atemperature of the battery pack is conventionally performed by settingthe maximum output limit of the battery pack simply on the basis of atemperature or by setting the maximum output limit of the battery packsimply through a voltage of the battery pack.

According to the conventional technique of calculating the maximumoutput value of a battery pack simply on the basis of a batterytemperature or a voltage of the battery pack, the maximum output valueis calculated using a table including a temperature or battery packvoltage and a battery pack output limit.

In other words, in order to reset the battery pack output limit, anadditional table indicating a relationship between a temperature orvoltage and a battery pack output limit should be stored.

To solve this problem, the present invention proposes a method in whichonly a maximum voltage and minimum voltage are checked in real time inbattery modules connected in series or parallel and the maximum outputlimit of an entire battery pack is set on the basis of the maximumvoltage and the minimum voltage without using the additional tableincluding a temperature or voltage and a battery pack output limit.(Prior Art Document) Korean Patent Application Laid-open Publication No.2010-0073973 A

DISCLOSURE OF THE INVENTION Technical Problem

The present invention provided a method for setting a maximum outputlimit of a battery pack in real time.

Furthermore, the present invention provided a method for setting amaximum output limit of a battery pack without an additional pre-storedtable of a maximum output limit according to a temperature and SOC.

Technical Solution

A method for setting a charging power limit of a battery when chargingthe battery having a plurality of battery cells, according to anembodiment of the present invention, includes: a reference chargingpower limit setting step in which a referential predetermined chargingpower limit is set; a real-time charging power limit setting step inwhich a real-time charging power limit is calculated in real timeaccording to a current voltage of the battery to set a real-timecharging power limit of the battery; and a charging power limitrestoring step in which the real-time charging power limit set in thereal-time charging power limit setting step is restored to thereferential predetermined charging power limit.

The real-time charging power limit setting step may include: (a-1) astep of measuring a voltage of each of the plurality of battery cells;(b-1) a step of determining whether the voltage of a battery cell havinga highest voltage among voltages of the plurality of battery cellsmeasured in step (a-1) exceeds a preset maximum allowable voltage; (c-1)a step of measuring a period during which the voltage of the batterycell having the highest voltage exceeds the preset maximum allowablevoltage; and (d-1) a step of setting the real-time charging power limitto a value obtained by reducing the referential battery charging powerlimit by a predetermined ratio when the period during which the voltageof the battery cell having the highest voltage exceeds the presetmaximum allowable voltage is equal to or longer than a predeterminedperiod in step (c-1), wherein steps (a-1) to (d-1) may be repeatedlyperformed, and the number of times step (d-1) is performed may becounted to generate a counted value.

In step (d-1), the predetermined ratio by which the referential batterycharging power limit is reduced may vary according to the counted value,wherein the counted value may be limited to a predetermined value, andwhen the counted value reaches the predetermined value, charging of thebattery may be stopped.

The counted value may increase by 1 every time step (d-1) is performedonce, and may decrease by 1 when the battery which is in a chargingstate switches to a discharging state.

In the charging power limit restoring step, the battery charging powerlimit may be restored to the referential predetermined charging powerlimit in any one case among: a case where the counted value is 0: a casewhere a current does not flow in the battery for at least apredetermined time; and a case where an SOC value of the battery reachesa predetermined reference SOC value.

A method for setting a discharging power limit of a battery whendischarging the battery having a plurality of battery cells, accordingto an embodiment of the present invention, includes: a referencedischarging power limit setting step in which a referentialpredetermined discharging power limit is set; a real-time dischargingpower limit setting step in which a real-time discharging power limit iscalculated in real time according to a current voltage of the battery toset a real-time discharging power limit of the battery; and adischarging power limit restoring step in which the real-timedischarging power limit set in the real-time discharging power limitsetting step is restored to the referential predetermined dischargingpower limit.

The real-time discharging power limit setting step may include: (a-2) astep of measuring a voltage of each of the plurality of battery cells;(b-2) a step of determining whether the voltage of a battery cell havinga lowest voltage among voltages of the plurality of battery cellsmeasured in step (a-2) is less than a preset minimum allowable voltage;(c-2) a step of measuring a period during which the voltage of thebattery cell having the lowest voltage is maintained less than thepreset minimum allowable voltage; and (d-2) a step of reducing thereferential predetermined battery discharging power limit by apredetermined ratio to calculate the real-time discharging power limitwhen the period during which the voltage of the battery cell having thelowest voltage is maintained less than the preset minimum allowablevoltage is equal to or longer than a predetermined period, wherein steps(a-2) to (d-2) may be repeatedly performed, and the number of times step(d-2) is performed may be counted to generate a counted value.

In step (d-2). the predetermined ratio by which the referential batterycharging power limit is reduced may vary according to the counted value,wherein the counted value may be limited to a predetermined value, andwhen the counted value reaches the predetermined value, discharging ofthe battery may be stopped.

The counted value may increase by 1 every time step (d-2) is performedonce, and may decrease by 1 when the battery which is in a dischargingstate switches to a charging state.

In the charging power limit restoring step, the battery dischargingpower limit may be restored to the referential predetermined dischargingpower limit in any one case among: a case where the counted value is 0;a case where a current does not flow in the battery for at least apredetermined time; and a case where an SOC value of the battery reachesa predetermined reference SOC value.

Advantageous Effects

According to the present invention, a maximum output limit of a batterypack may be set in real time.

Furthermore, a maximum output limit of a battery pack may be set withoutan additional pre-stored table of a maximum output limit according to atemperature and SOC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a method for setting a batterycharging power limit at the time of charging according to an embodimentof the present invention.

FIG. 2 is a detailed flowchart illustrating a real-time charging powerlimit setting step of the method for setting a battery charging powerlimit at the time of charging according to an embodiment of the presentinvention.

FIG. 3 is a flowchart illustrating a method for setting a batterydischarging power limit at the time of discharging according to anembodiment of the present invention.

FIG. 4 is a detailed flowchart illustrating a real-time charging powerlimit setting step of the method for setting a battery discharging powerlimit at the time of discharging according to an embodiment of thepresent invention.

FIG. 5 is a graph illustrating that a voltage of a battery cell isrestored by setting a battery discharging power limit at the time ofdischarging according to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings so that those skilledin the art can easily carry out the present invention. However, thepresent invention may be implemented in various different forms and isnot limited to the embodiments described herein. Some parts of theembodiments, which are not related to the description, are notillustrated in the drawings in order to clearly describe the embodimentsof the present invention. Like reference numerals refer to like elementsthroughout the description.

The term “first”, “second” or the like may be used for describingvarious elements but does not limit the elements. Such terms are onlyused for distinguishing one element from other elements. For example,without departing the scope of the present invention, a first elementmay be referred to as a second element, and likewise, a second elementmay be referred to as a first element. The terminology used herein isnot for delimiting the present invention but for describing specificembodiments. The terms of a singular form may include plural formsunless otherwise specified.

In the entire description, when one part is referred to as being“connected” to another part, the former may be “directly connected” tothe latter or “electrically connected” thereto via an intervening otherpart. When it is mentioned that a certain part “includes” or “comprises”certain elements, the part may further include other elements, unlessotherwise specified. The term “step (ing) . . . ” or “step of . . . ”used herein does not represent “step for . . . ”.

The terms used herein have been selected from among general terms thatare widely used at the present time in consideration of the functions ofthe present invention, but may be changed depending on intentions ofthose skilled in the art, judicial precedents, or the advent of newtechnology. Furthermore, specific terms have been arbitrarily selectedby the applicant, and the meanings of such terms will be described indetail in relevant sections of the description. Therefore, it should beunderstood that the terms used herein should not be simply definedliterally but should be defined on the basis of the meanings of theterms and the overall contents of the present disclosure.

1. Method for Setting a Battery Power Limit at the Time of ChargingAccording to an Embodiment of the Present Invention

FIG. 1 is a flowchart illustrating the method for setting a batterycharging power limit at the time of charging according to an embodimentof the present invention.

FIG. 2 is a detailed flowchart illustrating a real-time charging powerlimit setting step of the method for setting a battery charging powerlimit at the time of charging according to an embodiment of the presentinvention.

The method for setting a battery power limit at the time of chargingaccording to an embodiment of the present invention will be describedwith reference to FIGS. 1 and 2.

The method for setting a battery power limit at the time of chargingaccording to an embodiment of the present invention may include areference charging power limit setting step in which a referentialpredetermined charging power limit is set (S110), a real-time chargingpower limit setting step in which a real-time charging power limit iscalculated in real time according to a current voltage of a battery toset a real-time charging power limit of the battery (S120), and acharging power limit restoring step in which the real-time chargingpower limit set in the real-time charging power limit setting step isrestored to the referential predetermined charging power limit (S130).

In detail, the battery may include a plurality of battery cells, and thereference charging power limit setting step may be set to apredetermined value according to specifications of each of the pluralityof battery cells included in the battery and entire batteryspecifications when designing the battery.

Meanwhile, the real-time charging power limit setting step (S120) mayinclude (a-1) a step of measuring a voltage of each of the plurality ofbattery cells (S121), (b-1) a step of determining whether the voltage ofa battery cell having a highest voltage exceeds a preset maximumallowable voltage (S122), (c-1) a step of measuring a time during whichthe voltage of the battery cell having the highest voltage exceeds thepreset maximum allowable voltage (S123), (d-1) a step of setting thereal-time charging power limit to a value obtained by reducing thereferential battery charging power limit by a predetermined ratio when aperiod during which the voltage of the battery cell having the highestvoltage exceeds the preset maximum allowable voltage is equal to orlonger than a predetermined period in step (c-1) (S124).

Meanwhile, in the real-time charging power limit setting step (S120),steps (a-1) to (d-1) may be repeatedly performed.

Meanwhile, the period during which the voltage of the battery cellhaving the highest voltage exceeds the preset maximum allowable voltagemay be measured from a point of time at which the voltage of the batterycell initially exceeds the preset maximum allowable voltage.

Hereinafter, the real-time charging power limit setting step will bedescribed with a specific embodiment. Step (b-1) may be a step ofdetermining whether the voltage of the battery cell having the highestvoltage, among the plurality of battery cells, exceeds 4.2 V. In step(c-1), when there is a battery cell having a voltage which exceeds 4.2 Vin step (b-1), a period during which the voltage of the battery cellexceeds 4.2 V may be measured. Meanwhile, in step (d-1), when the periodduring which the voltage of the battery cell exceeds 4.2 V is at least 5seconds, the battery charging power limit may be reset.

Meanwhile, in the real-time charging power limit setting step, thenumber of times step (d-1) is performed is counted by a counting moduleto generate a counted value.

Meanwhile, in step (d-1), the predetermined ratio by which thereferential battery charging power limit is reduced varies according tothe counted value, wherein the counted value is limited to apredetermined value, and when the counted value reaches thepredetermined value, charging of the battery may be stopped.

In detail, the predetermined ratio according to the counted value may becalculated using the following equation.

Predetermined ratio=0.8^(counted value)

Furthermore, the predetermined value to which the counted value islimited may be 10.

In other words, when the counted value is limited to 10, thepredetermined ratio is 0.810 according to the above equation, and may beabout 1/10 of the reference charging power limit of a battery pack.

Meanwhile, the counted value may increase by 1 every time step (d-1) isperformed once, and may decrease by 1 every time the battery which is ina charging state switches to a discharging state.

Meanwhile, in the charging power limit restoring step, the batterycharging power limit may be restored to the referential predeterminedcharging power limit in any one case among a case where the countedvalue is 0, a case where a current does not flow in the battery for atleast a predetermined time, and a case where an SOC value of the batteryreaches a predetermined reference SOC value.

On the basis of the above description, the method for setting a batterycharging power limit at the time of charging according to an embodimentof the present invention may easily calculate the charging power limitof the battery pack without an additional table in which a temperatureor voltage and a charging power limit are set.

That is, without storing an additional table in which a temperature orvoltage and a charging power limit are set, the charging power limit ofthe battery pack may be set. Furthermore, without directly measuring atemperature of the battery pack, the charging power limit of the batterypack may be calculated.

2. Method for Setting a Battery Discharging Power Limit at the Time ofDischarging According to an Embodiment of the Present Invention

FIG. 3 is a flowchart illustrating the method for setting a batterydischarging power limit at the time of discharging according to anembodiment of the present invention.

FIG. 4 is a detailed flowchart illustrating a real-time charging powerlimit setting step of the method for setting a battery discharging powerlimit at the time of discharging according to an embodiment of thepresent invention.

The method for setting a battery discharging power limit at the time ofdischarging according to an embodiment of the present invention will bedescribed with reference to FIGS. 3 and 4.

The method for setting a battery discharging power limit at the time ofdischarging according to an embodiment of the present invention mayinclude a reference discharging power limit setting step in which areferential predetermined discharging power limit is set (S210), areal-time discharging power limit setting step in which a real-timedischarging power limit is calculated in real time according to acurrent voltage of a battery to set a real-time discharging power limitof the battery (S220), and a discharging power limit restoring step inwhich the real-time discharging power limit set in the real-timedischarging power limit setting step is restored to the referentialpredetermined discharging power limit (S230).

In detail, the battery may include a plurality of battery cells, and thereference discharging power limit setting step may be set to apredetermined value according to specifications of each of the pluralityof battery cells included in a battery pack and entire battery packspecifications when designing the battery pack.

Meanwhile, the real-time discharging power limit setting step (S220) mayinclude (a-2) a step of measuring a voltage of each of the plurality ofbattery cells (S221), (b-2) a step of determining whether the voltage ofa battery cell having a lowest voltage, among the plurality of batterycells, is less than a preset minimum allowable voltage (S222), (c-2) astep of measuring a time during which the voltage of the battery cellhaving the lowest voltage is less than the preset minimum allowablevoltage (S223), (d-2) a step of reducing the referential batterydischarging power limit by a prescribed ratio to calculate the real-timedischarging power limit when a period during which the voltage of thebattery cell having the lowest voltage is less than the preset minimumallowable voltage is equal to or longer than a predetermined period instep (c-2) (S224).

Meanwhile, in the real-time discharging power limit setting step (S220),steps (a-2) to (d-2) may be repeatedly performed.

Meanwhile, the period during which the voltage of the battery cellhaving the lowest voltage is less than the preset minimum allowablevoltage may be measured from a point of time at which the voltage of thebattery cell is initially less than the preset minimum allowablevoltage.

Hereinafter, the real-time discharging power limit setting step will bedescribed with a specific embodiment. Step (b-2) may be a step ofdetermining whether the voltage of the battery cell having the lowestvoltage, among the plurality of battery cells, is less than 3.0 V. Instep (c-2), when there is a battery cell having a voltage which is lessthan 3.0 V in step (b-2), a time during which the voltage of the batterycell is less than 3.0 V may be measured. Meanwhile, in step (d-2), whenthe time during which the voltage of the battery cell is less than 3.0 Vis at least 5 seconds, the battery discharging power limit may be reset.

Meanwhile, in the real-time discharging power limit setting step, thenumber of times step (d-2) is performed is counted by a counting moduleto generate a counted value.

Meanwhile, in step (d-2), the predetermined ratio by which thereferential battery discharging power limit is reduced varies accordingto the counted value, wherein the counted value is limited to apredetermined value, and when the counted value reaches a predeterminedvalue, discharging of the battery may be stopped.

In detail, the predetermined ratio according to the counted value may becalculated using the following equation.

Predetermined ratio=0.8^(counted value)

Furthermore, the predetermined value to which the counted value islimited may be 10.

In other words, when the counted value is limited to 10, thepredetermined ratio is 0.810 according to the above equation, and may beabout 1/10 of the reference discharging power limit of a battery pack.

Meanwhile, the counted value may increase by 1 every time step (c-2) isperformed once, and may decrease by 1 every time the battery which is ina discharging state switches to a charging state.

Meanwhile, in the discharging power limit restoring step, the batterydischarging power limit may be restored to the referential predetermineddischarging power limit in any one case among a case where the countedvalue is 0, a case where a current does not flow in the battery for atleast a predetermined time, and a case where an SOC value of the batteryreaches a predetermined reference SOC value.

On the basis of the above description, the method for setting a batterydischarging power limit at the time of discharging according to anembodiment of the present invention may easily calculate the dischargingpower limit of the battery pack without an additional table in which atemperature or voltage and a discharging power limit are set.

That is, without storing an additional table in which a temperature orvoltage and a discharging power limit are set, the discharging powerlimit of the battery pack may be set. Furthermore, without directlymeasuring a temperature of the battery pack, the discharging power limitof the battery pack may be calculated.

Furthermore, referring to FIG. 5, when the discharging power limit ofthe battery is reduced, a cell voltage is restored, and thus the usetime of the battery may increase.

Although the method for controlling battery power limit has beendescribed with reference to the specific embodiments, it is not limitedthereto. Therefore, it will be readily understood by those skilled inthe art that various modifications and changes can be made theretowithout departing from the spirit and scope of the present inventiondefined by the appended claims.

1. A method for setting a charging power limit of a battery whencharging the battery, wherein the battery includes a plurality ofbattery cells, the method comprising: a reference charging power limitsetting step of setting a referential predetermined charging powerlimit; a real-time charging power limit setting step of calculating areal-time charging power limit in real-time according to a real-timevoltage of the battery and setting a real-time charging power limit ofthe battery; and a charging power limit restoring step of restoring thereal-time charging power limit set in the real-time charging power limitsetting step to the referential predetermined charging power limit. 2.The method of claim 1, wherein the real-time charging power limitsetting step comprises: (a-1) a step of measuring a voltage of each ofthe plurality of battery cells; (b-1) a step of determining whether thevoltage of a battery cell having a highest voltage among voltages of theplurality of battery cells measured in step (a-1) exceeds a presetmaximum allowable voltage; (c-1) a step of measuring a period duringwhich the voltage of the battery cell having the highest voltage exceedsthe preset maximum allowable voltage; and (d-1) a step of setting thereal-time charging power limit to a value obtained by reducing thereferential predetermined charging power limit by a predetermined ratiowhen the period during which the voltage of the battery cell having thehighest voltage exceeds the preset maximum allowable voltage is equal toor longer than a predetermined period in step (c-1), wherein steps (a-1)to (d-1) are repeatedly performed, and wherein a number of times step(d-1) is performed is counted to generate a counted value.
 3. The methodof claim 2, wherein, in step (d-1), the predetermined ratio by which thereferential battery charging power limit is reduced varies according tothe counted value, and wherein the counted value is limited to apredetermined value, and when the counted value reaches thepredetermined value, charging of the battery is stopped.
 4. The methodof claim 2, wherein the counted value increases by 1 every time step(d-1) is performed once, and decreases by 1 when the battery which is ina charging state switches to a discharging state.
 5. The method of claim4, wherein, in the charging power limit restoring step, the real-timecharging power limit is restored to the referential predeterminedcharging power limit in any one case among: a case where the countedvalue is 0; a case where current does not flow in the battery for atleast a predetermined time; and a case where an SOC value of the batteryreaches a predetermined reference SOC value.
 6. A method for setting adischarging power limit of a battery when discharging the battery,wherein the battery includes a plurality of battery cells, the methodcomprising: a reference discharging power limit setting step of settinga referential predetermined discharging power limit; a real-timedischarging power limit setting step of calculating a real-timedischarging power limit in real-time according to a real-time voltage ofthe battery and setting a real-time discharging power limit of thebattery; and a discharging power limit restoring step of restoring thereal-time discharging power limit set in the real-time discharging powerlimit setting step to the referential predetermined discharging powerlimit.
 7. The method of claim 6, wherein the real-time discharging powerlimit setting step comprises: (a-2) a step of measuring a voltage ofeach of the plurality of battery cells; (b-2) a step of determiningwhether the voltage of a battery cell having a lowest voltage amongvoltages of the plurality of battery cells measured in step (a-2) isless than a preset minimum allowable voltage; (c-2) a step of measuringa period during which the voltage of the battery cell having the lowestvoltage is maintained less than the preset minimum allowable voltage;and (d-2) a step of reducing the referential predetermined batterydischarging power limit by a predetermined ratio to calculate thereal-time discharging power limit when the period during which thevoltage of the battery cell having the lowest voltage is maintained lessthan the preset minimum allowable voltage is equal to or longer than apredetermined period, wherein steps (a-2) to (d-2) are repeatedlyperformed, and wherein a number of times step (d-2) is performed iscounted to generate a counted value.
 8. The method of claim 7, wherein,in step (d-2), the predetermined ratio by which the referential batterydischarging power limit is reduced varies according to the countedvalue, and wherein the counted value is limited to a predeterminedvalue, and when the counted value reaches the predetermined value,discharging of the battery is stopped.
 9. The method of claim 7, whereinthe counted value increases by 1 every time step (d-2) is performedonce, and decreases by 1 when the battery which is in a dischargingstate switches to a charging state.
 10. The method of claim 9, wherein,in the discharging power limit restoring step, the real-time dischargingpower limit is restored to the referential predetermined dischargingpower limit in any one case among: a case where the counted value is 0;a case where current does not flow in the battery for at least apredetermined time; and a case where an SOC value of the battery reachesa predetermined reference SOC value.